The objectives of this proposed work are three-fold: 1. To corroborate in a larger prospective study our presently completed feasibility study in 45 patients. This study illustrates that dexamethasone suppression adrenal scintiscanning with radioiodinated cholesterol reveals 4 anatomical-functional imaging patterns in patients with low renin essential hypertension: 1. Uptake of I-131 in one adrenal only is found in an adenoma of one adrenal cortex. 2. Symmetrical uptake early and late is found in macronodular hyperplasia of the adrenal cortex. 3. Symmetrical uptake four days or more after tracer administration is found in micronodular hyperplasia. 4. No uptake in either adrenal early or late is found when the adrenal cortices are normal. Blood pressure falls to normal during the administration of spironolactone when the adrenal cortex is abnormal as recognized by scintiscanning but does not respond significantly to spironolactone when the adrenal cortex is normal. 2. To synthesize, develop and evaluate radiolabeled inhibitors of enzymes in adrenal glands would decrease the time required for imaging and the radiation dose in comparison to the currently used radioiodinated cholesterols. 3. To synthesize, develop and evaluate the anatomical-functional imaging capabilities of radiolabeled neuronal blocking agents, and reversible inhibitors of enzymes in the adrenal medulla. The diagnostic capabilities of the most successful of these radiolabeled imaging agents will be analyzed first in patients most at risk for disease of the adrenal medulla, then in patients with normal and high renin hypertension.